[POWERPC] pseries: device node status can be "ok" or "okay"

It seems that some versions of firmware will report a device
node status as the string "okay". As we are not expecting this
string, the device node will be ignored by the EEH subsystem.
Which means EEH will not be enabled.

When EEH is not enabled, PCI errors will be converted into
Machine Check exceptions, and we'll have a very unhappy system.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>